The main difficulty in treating urinary stones is due to the fact that the stone formation itself is a complex process. In the past certain insoluble aluminum compounds, in particular aluminum hydroxide gels and aluminum carbonate gels, have been tested in patients with phosphate stones, but without impressive results, as can be seen from publications such as: E. Hienzsch u. H. J. Schneider, Der Harnstein, Gustav Fischer-Verlag Jena, 1973; E. Shorr u. A. C. Carter, J.A.M.A., 144, 1549-56 (1950); H. Kracht, A. A. Kollwitz, E. Lohe, Der Urologe, S. 1-6 (1970); Th. Friis u. E. Weeke, Acta med. scand., Vol. 187, 41-48 (1970); H. Studer, Helv. Chirurgica Acta, 23, 130 (1956); E. Shorr, Journ., Urolog., 53, 507-(1945); L. S. Goodman u. A. Gilman, The Pharmacological Basis of Therapeutics (4th Edition); M. Lotz et al., New Engl. J. Med. 409-415 (1968); and DOS (German Published Specifications) Nos. 1,921,999; 2,152,228; 2,201,752; and 2,406,120.
The action of these compounds is based upon the reduction of the absorption of phosphate from the diet, because, when aluminum hydroxide gels or aluminum carbonate gels are administered orally, phosphate addition products form in the intestine, which are eliminated with the feces. The unsatisfactory results obtained hitherto with the present method of treatment are due to the fact that the phosphate binding capacities of the aluminum compounds that have been tried have proven to be unreliable and insufficiently active. This is why they have had to be administered in such high doses, and this causes disturbances in the stomach and intestinal tract; often they have produced an undesirable simultaneous binding of stomach acid. Due to their low capacity for the binding of phosphate, these compounds are not easily controllable, so that, if they are administered in large volume they can cause a complete removal of the phosphate from the food the patient consumes, a certain amount of phosphates being necessary in the diet for metabolic equilibrium. The preparations containing these compounds are offered mainly in the form of gels or emulsions, the patient being required to carry about with him and consume unreasonable amounts of medication; in the case of other, dry preparations, the number of tablets that must be consumed is greater than reasonable. Most of the aluminum compounds presently available also undesirably raise the pH of the urine, and thus cause phosphate supersaturation, thereby augmenting the tendency towards crystallization.
Thus, there arises the necessity to create an aluminum compound whose capacity for binding phosphate will be several times higher than that of those known hitherto, one which will produce no appreciable changes in the pH of the stomach, will permit better control, and above all will be usable in smaller amounts in dry product form, and one which will not result in any significant increase in the pH of the urine and will not lose its activity through the aging of the aluminum compound.